The goal of this research program is to contribute to our understanding of the properties and central action of Golgi tendon organs. This sense organ is found almost as plentifully as its companion receptor, the muscle spindle, in the majority of mammalian striated muscles. Input from both receptor types is thought to contribute significantly to both motor control and kinesthesia. However, despite some valuable recent work less is known about the properties of tendon organs than of spindles. Furthermore, and in sharp contrast to at least the monsynaptic central projections and actions of spindles, there is much confusion and uncertainty about the central projections and actions of tendon organs. The specific aims of this proposal are to help rectify these deficits with an emphasis on the segmental actions of tendon organs. In long range goals, I plan to continue this effort in studies that address supraspinal and plastic aspects of motor control. It also bears emphasis that many neurological diseases involve hyperactivity of spinal reflex pathways and that many neuromuscular diseases involve degeneration of alpha axons with subsequent changes in the motor unit-muscle receptor interactions at both peripheral and central levels of the nervous system. For these reasons my studies will hopefully provide information required for a better understanding of spasticity and rigidity and diseases such as ALS, adult spinal muscular atrophy, Friederich's ataxia, and those of Werdnig-Hoffman, Kugelberg-Welander, and Charcot-Marie Tooth.